In a city known for its history, local jeweler M.S. Rau Antiques is making history with the 10.06-carat blue diamond called The Royal Blue. It's a rarity because of its cut, color, carat and clarity.

"99.9 percent of blue diamonds are under 1 carat, so 1/1,000th of them are over a carat. This one is over 10 carats. So to the best of our knowledge, it's the only 10-carat blue diamond for sale in the entire world," said Rau.

The asking price is $9.85 million.

"With any color diamond, it's the color of the stone that makes it valuable. The cut on the stone, which is radiant, is the ideal cut for bringing out the perfect color to it," Rau said.

However, the stone didn't always look this way.

"This was actually in an antique setting, and it was 14 carats. We bought it and when we saw it we thought it could be a fancy blue. It was cut poorly, because it was cut hundreds of years ago when they didn't know how to achieve that magnificent, fancy blue color," said Rau.

Rau wanted to cut it down to enhance the color. But that was a difficult decision, because it could split or crack as it does in one in 5,000 cases. Fortunately, in this case, that didn't happen.

A radiant cut brought out the stone's sparkle even more.

"It's a great cut for a color diamond, because it has more facets. It has 70 facets as opposed to a brilliant cut which has 57 facets," said Susan Lapene, who is a diamond specialist there.

"The light travels in, and it bounces around all these facets like a fun house of mirrors, and then it comes out of the top," said Lapene.

The Royal Blue is on display with many one of a kind pieces of jewelry and furniture for sale.

Rau showed us a chair from Versailles palace and then took us to a room filled with priceless art including Monet, Renoir and Van Gogh paintings.

"We're very proud of owning the best things and to have them here in New Orleans and on Royal Street. To have what we feel to be the single biggest gemstone for sale in the entire world is pretty exciting," said Rau.

The blue diamond is made by the absence of nitrogen. It has boron in it and nothing else. It's from the same India mines as the famed Hope diamond, which is in the Smithsonian. There's also a blue diamond in the British Royal Crowns.

ITEM, IN THE FRENCH QUARTER, IS DRAWING ATTENTION AROUND THE GLOBE. W-D-S-U ANCHOR RACHEL WULFF HAS MORE ON THE ROYAL BLUE DIAMOND... AND HOW IT COULD BE YOURS...FOR A PRICE. 10:17 this is as good as it gets.. ITS BEAUTY IS MESMERIZING... 22:19 it's called the royal blue 22:23 IN A CITY KNOWN FOR IT'S HISTORY.. LOCAL JEWELER M.S. RAU ANTIQUES IS MAKING HISTORY..WITH THIS 10.06 CARAT BLUE DIAMOND... A RARITY... 10:37 99.9 percent of blue diamonds are under 1 carat..so 1/1000th of them are over a carat. This one is over 10 carats.. To the best of our knowledge it's the only 10 carat diamond blue diamond for sale in the entire world. 50 THE ASKING PRICE--9.8 MILLION DOLLARS. 12:40 with any color diamond.. It's the color of the stone that makes it valuable. The cut on the stone which is radiant. Is the ideal cut for bringing out the perfect color to it.49 HOWEVER THE STONE DIDN'T ALWAYS LOOK THIS WAY.. 30:50 when they bought the royal blue. It was 14 carats. They wanted to cut it down to enhance the color. But that was a difficult decision, because it could split or crack as it does in one in 5000 cases. Fortunately in this case.. That didn't happen. 31:02 A RADIANT CUT BROUGHT OUT THE STONE'S SPARKLE EVEN MORE. 21:12 it's a great cut for a color diamond because it has more facets. It has 70 facets.. As opposed to a brilliant cut which has 57 facets 20 21:25 the light travels in.. It bounces around..all these facets like a fun house of mirrors and then it comes out of the top31 THE ROYAL BLUE IS ON DISPLAY ALONG WITH MANY FINE PIECES OF JEWELRY....AND ONE OF A KIND PIECES FOR SALE .. 15:23 this is a chair from versailles palace INCLUDING THESE MONET, RENOIR AND VAN GOGH PAINTINGS... 13:22 we're very proud of owning the best things and to have here in new orleans and on royal street. To have what we feel to be the single biggest gemstone for sale in the entire world..is pretty exciting. 33 ON YOUR SIDE IN THE FRENCH QUARTER, RACHEL WULFF WDSU NEWS. THE BLUE DIAMOND IS MADE BY THE ABSENCE OF NITROGEN....IT HAS BORON IN IT AND NOTHING ELSE ITS FROM THE SAME INDIA MINES AS THE FAMED HOPE DIAMOND WHICH IS IN THE SMITHSONIAN. THERE'S ALSO A BLUE DIAMOND IN THE BRITISH ROYAL CROWNS.